The present invention relates to flat substrate polishing and Chemical-Mechanical-Planarization (CMP) polishing pad conditioning heads or disks. The invention may be used to condition a unique class of CMP polishing pads that incorporate areas of fixed abrasive material on the polishing pad to eliminate the need for abrasive-containing slurries in the polishing of both dielectric and semiconductor (oxide) films and metal films on semiconductor wafers as well as wafers and disks used in computer hard disk drives. More specifically, this invention relates to continuous CVD diamond coated substrates having sufficient surface roughness for use in other abrasive sanding, grinding or polishing tools where very controlled and gentle abrasion is required.
CMP has become a critical process employed in the fabrication of high-density integrated circuits, disk drive heads and nano-fabricated components. The CMP process economics are a function of the costs for consumables employed, depreciation and yields. Traditionally slurries represent the largest component of process costs and a major source of yield losses due to the instability of the slurry solution. Other consumables employed in the CMP process include polishing pads, pad conditioners and various mechanical components of the polishing system.
A new class of xe2x80x9cfixed abrasivexe2x80x9d polishing pads has been developed that integrates abrasive material into the polishing pad, eliminating the need for a separate abrasive-containing slurry. An example of a fixed abrasive CMP pad is the 3M Slurry-Free CMP Pad #M3100, manufactured by 3M Corporation Superabrasives and Microfinishing Systems Division, consisting of a polymer pad with 40-micron tallxc3x97200-micron diameter pedestals comprised of 0.2-micron cerium oxide abrasive. The CMP polishing rate resulting from the use of these fixed abrasive pads is highly sensitive to the surface properties of the abrasive (e.g. cerium oxide) areas on the pads. The first application of these pads was for a particular type of integrated circuit, Dynamic Random Access Memory chips (DRAMs). It has been found that the surface roughness and hardness of the DRAMs actually conditions the fixed abrasive material until the polishing process is completed. This establishes a process that is self-limiting, minimizing the potential for xe2x80x9cover-polishing.xe2x80x9d In the process, after installing a new fixed abrasive pad, there is known to be a period, i.e. polishing of typically 5 to 20 wafers, during which the quality of polishing is low, and the wafer yield loss is very high due to the required period of pad conditioning, i.e. pad xe2x80x9cbreak-in.xe2x80x9d Therefore, expensive product wafers are destroyed during this break-in process, which is detrimental to manufacturing economics.
Traditional CMP pad conditioners employ relatively large, abrasive grit, which is bonded to a substrate using electroplated metal or various brazing materials. Additionally, Zimmer, U.S. Pat. No. 5,921,856 and Zimmer et al. U.S. Pat. No. 6,054,183 describe a class of CMP pad conditioners utilizing large, abrasive diamond grit bonded to a substrate with a CVD diamond film. For all of these CMP pad conditioning disk products, the grit particles are too large to effectively condition the surface of the fixed-abrasive polishing pads, and their use results in damage or extreme wear to the pad, short pad lifetimes, and unstable process conditions.
Tietz et al. European Patent Application EP 1 052 062 A1 discloses a method and apparatus for preconditioning fixed abrasive articles that employs an abrasive disk or pad comprised of a material having a surface roughness less than or equal to 0.20 micron, such as silicon carbide, alumina, silica, titania, copper, resist, and polymers. Tietz et al. do not contemplate the use of polycrystalline diamond, or any other chemical vapor deposited coated substrates as the abrasive disk.
The present invention overcomes these problems with prior art CMP pad conditioners, and is especially useful for conditioning fixed-abrasive polishing pads.
The product of the present invention allows fixed-abrasive CMP polishing pads to be preconditioned prior to wafer processing, resulting in minimization of yield losses after a new fixed abrasive pad is installed on a CMP system. The CMP pad conditioner of the present invention also allows wafer-processing yields to be further optimized.
In contrast to prior art pad conditioners, the conditioner of the present invention does not utilize a low distribution of large grit particles on the conditioner surface. Rather, the conditioner of the present invention is a unique CMP pad conditioner whose conditioning properties are controlled by a polycrystalline diamond surface microstructure. Using a layer of fine, polycrystalline diamond to create the abrasive surface, it is possible to fabricate the abrasive geometry needed to establish and maintain optimal polishing conditions for fixed-abrasive polishing pads. The surface hardness, crystalline orientation and average crystal dimensions control the properties of the conditioner such as the conditioning rate. The CMP process rate, pad lifetimes and process yields are optimized by controlling the surface microstructure of the conditioner in the present invention.
The present invention is directed to a polishing pad conditioning head for a CMP and similar types of apparatus that has been found especially useful in conditioning the surface of fixed abrasives in fixed-abrasive CMP polishing pads in the manner necessary for maintaining optimal process conditions for the planarization process on dielectric and metal films on semiconductor wafers, as well as wafers and disks used in computer hard disk drives.
In a CMP and similar apparatus, a polishing pad conditioning head is provided which comprises a substrate and a layer of polycrystalline diamond that is attached onto the substrate. Preferably, the polycrystalline diamond with a fine and controlled grain structure is deposited directly onto the substrate by chemical vapor deposition (CVD). By the term of xe2x80x9cchemical vapor deposition,xe2x80x9d it is intended to mean deposition of materials by vacuum deposition processes, including thermally-activated deposition from reactive gaseous precursor materials; and plasma, microwave plasma, and DC or RF plasma arc-jet deposition from gaseous precursor materials. Alternatively, a thin sheet of polycrystalline material may be deposited on a preferred growth substrate by a chemical vapor deposition process, then removed from the growth substrate and bonded to the CMP conditioning disk substrate by a variety of attachment or lamination methods known in the art. In contrast to other materials disclosed in the prior art, CVD diamond exhibits the highest hardness, extremely low chemical reactivity, and can be deposited with a highly controlled microstructure.